Have you ever been told that microwaving vegetables depletes their nutritional value? Anytime you cook a vegetable (regardless of the method) there is usually some nutrient loss, but the belief held by some is that microwaves destroy up to 90 percent of the nutrients in the food, whereas stovetop cooking can be as low as 10 percent. But is it true? Here's what we discovered:
According to a recent 'Ask Umbra' column on Grist, there are three factors affecting nutrient loss when you cook vegetables: temperature, time, and water. "Nutrients tend to be both heat-intolerant and water-soluble," the article says, which means that any method that requires a) cooking at a high temperature for a long time, and b) uses a lot of water will result in the greatest nutrient loss. (So by this measure, boiling vegetables is likely the worst offender.) It goes without saying then that cooking at a lower temperature for a shorter amount of time and with less water would result in the least amount of nutrients lost, and that's what the microwave accomplishes.
So where did this idea originate in the first place? According to Grist, in 2003 a study from Spain claimed that steaming broccoli in the microwave caused it to lose 97 percent of its antioxidants, while stovetop cooking only resulted in an 11 percent loss. But critics say the study used more water than would ever be necessary in a microwave, and thus the results were flawed.
Basically, water, not the microwave, is the most important factor when cooking vegetables, according to Grist. The less water, the better:
Steaming, for instance, is a fairly good option because the veggies have less contact with water. Even better: Cook your veggies in a stew or soup, and you'll be able to slurp those escapee nutrients up. Stovetop stir-frying or sautéing is also a good choice, assuming you don't go crazy with the oil. Baking and roasting are yummy, but don't forget that long exposures to heat will zap some of the nutrients...
Of course, other arguments against microwaves have to do with magnetrons and radiation levels, etc., which is a whole other topic. But as far as nutrient loss goes, if microwaving is your preferred choice for cooking vegetables, than cook on. Just watch the amount of water you use!
Read More: Ask Umbra: Does microwaving vegetables zap their nutritional value? | Grist
Related: How To Steam Broccoli in the Microwave
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I've always heard the opposite, that microwave cooking resulted in more nutrient retention because there is often less or no water and the cooking times are shorter.
I don't boil any vegetables. We generally steam or blanch.
Isn't blanching just boiling for short time and then cooling in ice bath? Sounds like a bad option for retaining the good stuff. Doesn't matter how long something is in boiling water, it's still contacting the same temperature.
Typically I do my veg in a frying pan, mostly because I don't have the patience to wait for water to boil just to use it for one minute. I like my veggies to have lots crunch and texture, so water in general is mostly out.
A link to the study - w00t! Cool, thanks. I've based my hatred of microwaves mostly on superstition - it just feels wrong. I think what affects the nutrients in vegetables is an important question, so thanks for addressing it. Too many people are obsessed with raw food forgetting that cooking it can help absorb the nutrients. I think a variety may be good.
I get that vegetables lose their nutrients when they are boiled. The nutrients leach out of the vegetables into the water. But when you just cook the vegetables (no water), where do the nutrients go?
@jess13, it does matter how long something is in boiling water, as chemical reactions don't happen in a time-independent manner. Most chemical breakdown occurs over long periods of time, which is one of the points made in the study. Exposing a chemical or nutrient to heat for 1 minute will cause substantially less breakdown than exposing it for 10 minutes.
Also, the time for contact with water is crucial. Like any solvent, water will extract all the water-soluble nutrition from vegetables, but this reaction also takes time. So blanching is a far better method, nutritionally speaking, than boiling. Also, the ice-bath stops the breakdown of nutrients.
Good thing roasting/grilling them tastes better, anyway! So excited that roast broccoli season is here again, mmmm.
They stay in the vegetable, or they "die" and are no longer effective
Sorry, I have to disagree. The article quoted begins with
In short, microwaves distort the molecular structure of the foods. They destroy much of the nutrients and cause many other problems with the immune system over a period of time. If you love your family read this and take the extra couple of minutes to heat the food up the right way.
http://www.globalhealingcenter.com/health-hazards-to-know-about/microwave-ovens-the-proven-dangers
(this comment is a response to Supreya's comment and linked article) The link from Supreya is just another article of microwave misinformation. A microwave oven will not "agitate" the molecules in the food and twist their molecular structure. Microwave ovens operate at a frequency tailored to the diatomic H2O molecule. The only molecule that a microwave will excite at a resonant frequency is a water molecule. That is how your microwave cooks food, by heating the H20 in the food. . If there is not sufficient water in the food, then the food will not heat. On the conventional side of cooking though, when cooking on a stove top or in a conventional oven, you are using infrared radiation instead of microwave radiation. Infrared will cook and burn the outer layers of food exposed to the radiation. when the H2O is cooked out of those layers. Burning creates charred carcinogenic particles that have been proven to cause cancer. With a microwave, the waves penetrate the food and heat the H2O inside the food as well as heating the outside layers. In this way, Microwaves allow quick, even heating without scorching or burning. Food does not "retain" the radiation and you do not "ingest" it.